1. Technical Field
This invention relates to a position detecting sensor that detects a position indicated by an indicator by detecting a change in the capacitance at the position indicated by the indicator, a position detecting device including this position detecting sensor, and a position detecting method used in these sensor and device.
2. Description of the Related Art
In recent years, indicator-detecting devices that utilize a capacitive sensing system as the system for detecting a position of an indicator used on a touch panel etc. have been vigorously developed. There are two types of capacitive sensing system, the surface type (Surface Capacitive Type) and the projected type (Projected Capacitive Type) systems. In both systems, a change in the capacitive coupling state between the sensor electrode and the indicator (e.g., finger, capacitive pen, etc.) is detected to detect a position of the indicator.
For example, in patent document 1 (Japanese Patent Laid-open No. 2009-265759), an indicator-detecting device that utilizes the capacitive sensing system of the surface type is introduced. An indicator-detecting device that utilizes the capacitive sensing system of the projected type may be configured by forming plural electrodes in a predetermined pattern on, e.g., a transparent substrate such as glass or a transparent film. The indicator-detecting device of the projected type detects a change in the capacitive coupling state between the indicator and the electrode when the indicator comes close to the electrode. Examples of the indicator-detecting device that utilizes the capacitive sensing system of the projected type are disclosed in, e.g., patent document 2 (Japanese Patent Laid-open No. 2003-22158), patent document 3 (Japanese Patent Laid-open No. Hei 9-222947), and patent document 4 (Japanese Patent Laid-open No. Hei 10-161795).
Furthermore, there has been proposed an indicator-detecting device that utilizes a system called the cross-point capacitive sensing system, which has been developed from the capacitive sensing system of the projected type.
FIG. 13 shows the schematic configuration of the sensor part in the indicator-detecting device that utilizes the cross-point capacitive sensing system. The indicator-detecting device that utilizes the cross-point capacitive sensing system is configured as a multi-touch-enabled device capable of simultaneously detecting plural indicators such as plural fingers.
In the position detecting sensor of this indicator-detecting device that utilizes the cross-point capacitive sensing system, plural upper electrodes Ex and plural lower electrodes Ey are disposed perpendicularly to each other in, e.g., the X-axis direction (horizontal direction) and the Y-axis direction (vertical direction) of the indication input surface. In this case, a predetermined capacitance Co (fixed capacitance) is formed at the overlapping part (cross-point) between the upper electrode Ex and the lower electrode Ey. Furthermore, at a position where an indicator fg such as a finger of the user is brought close to or into contact with the indication input surface, a capacitance Cf is formed between the electrodes Ex and Ey at this position and the indicator fg. In addition, the indicator fg such as a finger is connected through the human body to the ground via a predetermined capacitance Cg. As a result, due to the capacitances Cf and Cg, the electric charge between the upper electrode Ex and the lower electrode Ey changes at the position of this indicator fg. In the conventional indicator-detecting device that utilizes the cross-point capacitive sensing system, this change in the electric charge is detected and, therefore, a position indicated by the indicator on the indication input surface is identified.
In patent document 5 (Japanese Patent Laid-open No. 2010-79791), a capacitive-type input device capable of detecting an indicator other than the finger or a capacitive pen is disclosed. As shown in FIG. 14A, the indicator-detecting sensor of the input device disclosed in patent document 5 includes a first substrate 2, a flexible second substrate 3 opposed to the first substrate 2 with an air layer 4 interposed therebetween, a first electrode 5 formed over almost the entire surface of the first substrate 2 that is facing the second substrate 3, and plural second electrodes 6 formed on the surface of the second substrate 3 that is facing the first substrate 2.
In the indicator-detecting sensor of the input device disclosed in patent document 5, when the second substrate 3 is not pressed by the indicator, a capacitance C1 is formed between each of the plural second electrodes 6 and the first electrode 5 as shown in FIG. 14A.
When the second substrate 3 is pressed toward the first substrate 2 by the indicator, the second substrate 3 is bent toward the first substrate 2 at the pressed position, as shown by an arrow in FIG. 14B, because the second substrate 3 has flexibility. Thus, the distance between the first substrate 2 and the second substrate 3 becomes shorter and the capacitance formed by the first electrode 5 and the second electrode 6 at this part becomes C2, which is larger than the above-described C1. If further pressing is performed as shown by an arrow in FIG. 14C, the second electrode 6 comes into contact with the first electrode 5 to be in a conductive state.
In the input device of patent document 5, when the capacitance formed by the above-described first electrode 5 and second electrode 6 is detected to be larger than C1, the pressing input by the indicator to the second substrate 3 (pressed position) can be detected. In addition, it is disclosed that the pressing input at the pressed position can also be determined by detecting that the second electrode 6 comes into contact with the first electrode 5 to be in a conductive state.